Mass customization in additive manufacturing

ABSTRACT

A method for the production of an object by additive manufacturing includes inputting a boundary shape and desired mechanical properties for said object, subdividing said boundary shape into a plurality of adjacent work cells, providing a plurality of lattices in a database, each lattice of the database including a geometry and a mechanical property, filling a first one of said work cells with a lattice from the database, the lattice selected based on the correspondence of the mechanical properties of said lattice to said desired mechanical properties of said object, filling the remaining ones of said work cells with lattices from said database to produce a filled boundary shape, each said lattice selected based on: the correspondence of the mechanical properties of said lattice to the desired mechanical properties of the object, and the compatibility of adjacent lattices in adjacent work cells with one another.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/616,557, filed Nov. 25, 2019, now allowed, which is a 35 U.S.C. § 371national phase application of International Application Serial No.PCT/US2018/056842, filed Oct. 22, 2018, which claims priority to U.S.Provisional Application Ser. No. 62/579,346, filed Oct. 31, 2017, andU.S. Provisional Application Ser. No. 62/719,316, filed Aug. 17, 2018,the entire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention concerns additive manufacturing in general andmore particularly concerns methods and apparatus for the efficientproduction of customized objects that include composite latticestructures.

BACKGROUND OF THE INVENTION

A group of additive manufacturing techniques sometimes referred to as“stereolithography” create a three-dimensional object by the sequentialpolymerization of a light polymerizable resin. Such techniques may be“bottom-up” techniques, where light is projected into the resin onto thebottom of the growing object through a light transmissive window, or“top down” techniques, where light is projected onto the resin on top ofthe growing object, which is then immersed downward into the pool ofresin.

The recent introduction of a more rapid stereolithography techniqueknown as continuous liquid interface production (CLIP), coupled with theintroduction of “dual cure” resins for additive manufacturing, hasexpanded the usefulness of stereolithography from prototyping tomanufacturing (see, e.g., U.S. Pat. Nos. 9,211,678; 9,205,601; and9,216.546 to DeSimone et al.; and also in J. Tumbleston, D.Shirvanyants, N. Ermoshkin et al., “Continuous liquid interfaceproduction of 3D objects,” Science 347, 1349-1352 (published online 16Mar. 2015); see also Rolland et al., U.S. Pat. Nos. 9,676,963,9,453,142, and 9,598,606).

By obviating the need to make expensive injection molds—required for theproduction of many products—additive manufacturing now presents theopportunity to produce objects that are highly customized for particularindividuals or uses. However, the generation of highly customized datafiles remains time consuming, potentially computationally intensive, andhence expensive. Accordingly, there remains a need for new approaches tomass customization of products to be produced by additive manufacturing.

SUMMARY OF THE INVENTION

Various embodiments described herein provide a method for the rapidproduction of an object from a light-polymerizable resin by additivemanufacturing, including: (a) inputting into a processor a boundaryshape and a plurality of desired mechanical properties for said object:(b) subdividing said boundary shape into a plurality of adjacent workcells in the processor; (c) providing a plurality of lattices in adatabase, each lattice of the database including a geometry and amechanical property; (d) filling a first one of said work cells with alattice from the database, the lattice selected based on thecorrespondence of the mechanical properties of said lattice to saiddesired mechanical properties of said object; (e) filling the remainingones of said work cells with lattices from said database to produce afilled boundary shape in the processor, each said lattice selected basedon: (i) the correspondence of the mechanical properties of said latticeto the desired mechanical properties of the object, and (ii) thecompatibility of adjacent lattices in adjacent work cells with oneanother; then (f) producing said object by additive manufacturing (e.g.,by bottom-up or top-down stereolithography) from the light-polymerizableresin and the filled boundary shape.

In some embodiments, the method may include, after said filling step(e), the step of confirming that the mechanical properties of the filledboundary shape correspond to the desired mechanical properties for theobject, and, if not, then repeating step (e) with different latticesfrom said database in said work cells until the mechanical properties ofthe filled boundary shape correspond to the desired mechanicalproperties of said object.

In some embodiments, the method may include, prior to said producingstep (f), (and after said confirming step if present) the step of:performing a final manufacturing process simulation of said filledboundary shape as a check of manufacturability of said filled boundaryshape.

In some embodiments, said database includes a manufacturability scorefor said additive manufacturing step for each said lattice, and saidfilling steps (d)-(e) are carried out with preference for latticeshaving a higher manufacturability score.

In some embodiments, said object is rigid, flexible, or elastic.

Various embodiments described also provide an additive manufacturingsystem including (a) an additive manufacturing apparatus (e.g., a bottomup stereolithography apparatus, such as a continuous liquid interfaceproduction apparatus); (b) a processing device; and (c) a memorycomprising instructions which, when executed by the processing device,cause the processing device to carry out the method embodimentsdescribed herein with said additive manufacturing apparatus.

Various embodiments described also provide a computer program productincluding a non-transitory computer readable storage medium havingcomputer readable software code sections embodied in the medium, whichsoftware code sections are configured to carry out the methodembodiments described herein.

The foregoing and other objects and aspects of the present invention areexplained in greater detail in the drawings herein and the specificationset forth below. The disclosures of all United States patent referencescited herein are to be incorporated herein by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates an apparatus of the present invention.

FIG. 2 schematically illustrates a process of the present invention.

FIG. 3 schematically illustrates one embodiment of a product produced bya process of the present invention.

FIGS. 4A and 4B illustrate an example computer-generated rendering of alattice combination and a completed prototype produced by a process ofthe present invention.

FIG. 5 is a rear perspective view of an example corner bracketprimitive, prior to being filled with lattices by a process of thepresent invention.

FIG. 6 is a rear perspective view of the example corner bracket of FIG.5, partially converted to a lattice fill in a process of the presentinvention.

FIG. 7 is a rear perspective view of the example corner bracket of FIGS.5-6, fully converted to lattice fill by a process of the presentinvention.

FIG. 8 is a front perspective view of the example corner bracketprimitive of FIGS. 5-7.

FIG. 9 is a front perspective view of the example corner bracket ofFIGS. 5-8, partially lattice filled.

FIG. 10 is a front perspective view of the example corner bracket ofFIGS. 5-9, fully converted to lattice fill by the process of the presentinvention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention is now described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein; rather these embodiments are provided sothat this disclosure will be thorough and complete and will fully conveythe scope of the invention to those skilled in the art.

Like numbers refer to like elements throughout. In the figures, thethickness of certain lines, layers, components, elements or features maylie exaggerated for clarity. Where used, broken lines illustrateoptional features or operations unless specified otherwise.

1. Production by Additive Manufacturing (Overview)

Numerous polymerizable liquids (or “resins”) for use in additivemanufacturing are known and can be used in carrying out the presentinvention. See, e.g., U.S. Pat. No. 9,205,601 to DeSimone et al.

In some embodiments, the resin is a dual cure resin. Such resins aredescribed in, for example, Rolland et al., U.S. Pat. Nos. 9,676,963;9,598,606; and 9,453,142, the disclosures of which are incorporatedherein by reference. Resins may be in any suitable form, including “onepot” resins and “dual precursor” resins (where cross-reactiveconstituents are packaged separately and mixed together before use, andwhich may be identified as an “A” precursor resin and a “B” precursorresin). Particular examples of suitable resins include, but are notlimited to, Carbon, Inc. rigid polyurethane resin (RPU), flexiblepolyurethane resin (FPU), elastomeric polyurethane resin (EPU), cyanateester resin (CE), epoxy resin (EPX), or urethane methacrylate resin(UMA), all available from Carbon, Inc., 1089 Mills Way, Redwood City,Calif. 94063 USA.

Note that, in some embodiments employing “dual cure” polymerizableresins, the part, following manufacturing, may be contacted with apenetrant liquid, with the penetrant liquid carrying a furtherconstituent of the dual cure system, such as a reactive monomer, intothe part for participation in a subsequent cure. Such “partial” resinsare intended to be included herein.

Techniques for additive manufacturing are known. Suitable techniquesinclude bottom-up or top-down additive manufacturing, generally known asstereolithography. Such methods are known and described in, for example,U.S. Pat. No. 5,236,637 to Hull U.S. Pat. Nos. 5,391,072 and 5,529,473to Lawton, U.S. Pat. No. 7,438,846 to John, U.S. Pat. No. 7,892,474 toShkolnik, U.S. Pat. No. 8,110,135 to El-Siblani, U.S. Pat. No. 9,636,873to Joyce, and U.S. Pat. No. 9,120,270 to Chen et al. The disclosures ofthese patents are incorporated by reference herein in their entirety.

In some embodiments, the intermediate object is formed by continuousliquid interface production (CLIP). CLIP is known and described in, forexample, PCT Application Nos. PCT/US2014/015486 (published as U.S. Pat.No. 9,211,678 on Dec. 15, 2015); PCT/US2014/015506 (also published asU.S. Pat. No. 9,205,601 on Dec. 8, 2015), PCT/US2014/015497 (alsopublished as U.S. Pat. No. 9,216,546 on Dec. 22, 2015), and in J.Tumbleston, D. Shirvanyants, N. Ermoshkin et al., “Continuous liquidinterface production of 3D Objects,” Science 347, 1349-1352 (publishedonline 16 Mar. 2015). See also R. Janusziewcz et al., “Layerlessfabrication with continuous liquid interface production,” Proc. Natl.Acad. Sci. USA 113, 11703-11708 (Oct. 18, 2016). In some embodiments,CLIP employs features of a bottom-up three-dimensional fabrication asdescribed above, but the irradiating and/or said advancing steps arecarried out while also concurrently maintaining a stable or persistentliquid interface between the growing object and the build surface orwindow, which may be an optically transparent member, such as by: (i)continuously maintaining a dead zone of polymerizable liquid in contactwith said build surface, and (ii) continuously maintaining a gradient ofpolymerization zone (such as an active surface) between the dead zoneand the solid polymer and in contact with each thereof the gradient ofpolymerization zone comprising the first component in partially curedform. In some embodiments of CLIP, the optically transparent membercomprises a semipermeable member (e.g.. a fluoropolymer), and thecontinuously maintaining a dead zone is carried out by feeding aninhibitor of polymerization through the optically transparent member,thereby creating a gradient of inhibitor in the dead zone and optionallyin at least a portion of the gradient of polymerization zone. Otherapproaches for carrying out CLIP that can be used in the presentinvention and potentially obviate the need for a semipermeable “window”or window structure include utilizing a liquid interface comprising animmiscible liquid (see L. Robeson et al., WO 2015/164234, published Oct.29, 2015), generating oxygen as an inhibitor by electrolysis (see I.Craven et al., WO 2016/133759. published Aug. 25, 2016), andincorporating magnetically positionable particles to which thephotoactivator is coupled into the polymerizable liquid (see J. Rolland,WO 2016/145182, published Sep. 15, 2016).

After the intermediate three-dimensional object is formed, it isoptionally washed, optionally dried (e.g., air dried) and/or rinsed (inany sequence). In some embodiments it is then further cured, preferablyby heating (although further curing may in some embodiments beconcurrent with the first cure, or may be by different mechanisms suchas contacting to water, as described in U.S. Pat. No. 9,453,142 toRolland et al.).

2. Washing and Further Curing (Overview)

Objects as described above can be washed in any suitable apparatus,preferably with a wash liquid as described above.

Wash liquids that may be used to carry out the present inventioninclude, but are not limited to, water, organic solvents, andcombinations thereof (e.g., combined as co-solvents), optionallycontaining additional ingredients such as surfactants, chelants(ligands), enzymes, borax, dyes or colorants, fragrances, etc.,including combinations thereof. The wash liquid may be in any suitableform, such as a solution, emulsion, dispersion, etc.

In some preferred embodiments, where the residual resin has a boilingpoint of at least 90 or 100° C. (e.g., up to 250 or 300° C., or more),the wash liquid has a boiling point of at least 30° C., but not morethan 80 or 90° C. Boiling points are given herein for a pressure of 1bar or 1 atmosphere.

Examples of organic solvents that may be used as a wash liquid, or as aconstituent of a wash liquid, include, but are not limited to, alcohol,ester, dibasic ester, ketone, acid, aromatic, hydrocarbon, ether,dipolar aprotic, halogenated, and base organic solvents, includingcombinations thereof. Solvents may be selected in based, in part, ontheir environmental and health impact (see, e.g., GSK Solvent SelectionGuide 2009). In some embodiments, the wash liquid comprises ahydrofluorocarbon, hydrochlorofluorocarbon, or hydrofluoroether solvent,such as 1,1,1,2,3,4,4,5,5,5-decafluoropentane (Vertrel® XF, DuPont™Chemours), 1,1,1,3,3-Pentafluoropropane, 1,1,1,3,3-Pentafluorobutane,etc.

Any suitable wash apparatus can be used, including but not limited to aCarbon Inc. SMART WASHER™, available from Carbon, Inc., Redwood City,Calif., USA.

After washing, the object is in some embodiments further cured,preferably by heating or baking.

Heating may be active heating (e.g., in an oven, such as an electric,gas, solar oven or microwave oven, heated bath, or combination thereof),or passive heating (e.g., at ambient (room) temperature). Active heatingwill generally be more rapid than passive heating and in someembodiments is preferred, but passive heating—such as simply maintainingthe intermediate at ambient temperature for a sufficient time to effectfurther cure—is in some embodiments preferred.

In some embodiments, the heating step is carried out at at least a first(oven) temperature and a second (oven) temperature, with the firsttemperature greater than ambient temperature, the second temperaturegreater than the first temperature, and the second temperature less than300° C. (e.g., with ramped or step-wise increases between ambienttemperature and the first temperature, and/or between the firsttemperature and the second temperature).

For example, the intermediate may be heated in a stepwise manner at afirst temperature of about 70° C. to about 150° C., and then at a secondtemperature of about 150° C. to 200 or 250° C., with the duration ofeach heating depending on the size, shape, and/or thickness of theintermediate. In another embodiment, the intermediate may be cured by aramped heating schedule, with the temperature ramped from ambienttemperature through a temperature of 70 to 150° C., and up to a final(oven) temperature of 250 or 300° C., at a change in heating rate of0.5° C. per minute, to 5° C. per minute. (See, e.g., U.S. Pat. No.4,785,075 to Shimp.)

In some embodiments, the heating step is carried out in an inert gasatmosphere. Inert atmosphere ovens are known, and generally employ anatmosphere enriched in nitrogen, argon, or carbon dioxide in the ovenchamber. Suitable examples include but are not limited to thoseavailable from Grieve Corporation, 500 Hart Road, Round Lake, Ill.60073-2898 USA, Davron Technologies, 4563 Pinnacle Lane, Chattanooga,Tenn. 37415 USA, Despatch Thermal Processing Technology, 8860 207thStreet, Minneapolis, Minn. 55044 USA, and others.

In other embodiments, the heating step is carried out in an inert liquidbath. Suitable inert liquids may be aqueous liquids (i.e., pure water,salt solutions, etc.), organic liquids (e.g., mineral oil fluorinated,perfluorinated, and polysiloxane organic compounds such asperfluorohexane, perfluoro(2-butyl-tetrahydrofurane),perfluorotripentylamine, etc. (commercially available as PERFLUORINERT®inert liquids from 3M Company), and mixtures thereof. These inertliquids can be deoxygenated if necessary, such as by bubbling an inertgas such as nitrogen through the liquid, by boiling the inert liquid, bymixing oxygen-scavenging agents with the inert liquid medium (orcontacting them to one another), etc., including combinations thereof(see, e.g., U.S. Pat. No. 5,506,007 to Williams et al.).

In some embodiments, the further curing or heating step (whether carriedout in a liquid or gas fluid) is carried out at an elevated pressure(e.g., elevated sufficiently to reduce volatilization or out-gassing ofresidual monomers, prepolymers, chain extenders, and/or reactivediluents, etc.). Suitable pressure ranges are from 10 or 15 psi to 70 or100 psi, or more.

3. Systems and Apparatus

The foregoing can be combined into apparatus and methods for carryingout the present invention, as first schematically illustrated in FIG. 1.Such an apparatus includes a user interface 3 for inputting instructions(such as selection of an object to be produced, and selection offeatures to be added to the object), a controller 4, and astereolithography apparatus 5 such as described above. An optionalwasher (not shown) can be included in the system if desired, or aseparate washer can be utilized. Similarly, for dual cure resins, anoven (not shown) can be included in the system, although operatedseparate oven can also be utilized.

Connections between components of the system can be by any suitableconfiguration, including wired and/or wireless connections. Thecomponents may also communicate over one or more networks, including anyconventional, public and/or private, real and/or virtual, wired and/orwireless network, including the Internet.

The controller 4 may be of any suitable type, such as a general-purposecomputer. Typically the controller will include at least one processor 4a, a volatile (or “working”) memory 4 b, such as random-access memory,and at least one non-volatile or persistent memory 4 c, such as a harddrive or a flash drive. The controller 4 may use hardware, softwareimplemented with hardware, firmware, tangible computer-readable storagemedia having instructions stored thereon, and/or a combination thereof,and may be implemented in one or more computer systems or otherprocessing systems. The controller 4 may also utilize a virtual instanceof a computer. As such, the devices and methods described herein may beembodied in any combination of hardware and software that may allgenerally be referred to herein as a “circuit,” “module,” “component,”and/or “system.” Furthermore, aspects of the present invention may takethe form of a computer program product embodied in one or more computerreadable media having computer readable program code embodied thereon.

Any combination of one or more computer readable media may be utilized.The computer readable media may be a computer readable signal medium ora computer readable storage medium. A computer readable storage mediummay be, for example, but not limited to, an electronic, magnetic,optical, electromagnetic, or semiconductor system, apparatus, or device,or any suitable combination of the foregoing. More specific examples (anon-exhaustive list) of the computer readable storage medium wouldinclude the following: a portable computer diskette, a hard disk, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an appropriateoptical fiber with a repeater, a portable compact disc read-only memory(CD-ROM), an optical storage device, a magnetic storage device, or anysuitable combination of the foregoing. In the context of this document,a computer readable storage medium may be any tangible medium that cancontain, or store a program for use by or in connection with aninstruction execution system, apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device. Program codeembodied on a computer readable signal medium may be transmitted usingany appropriate medium, including but not limited to wireless, wireline,optical fiber cable, RF, etc., or any suitable combination of theforegoing.

The at least one processor 4 a of the controller 4 may be configured toexecute computer program code for carrying out operations for aspects ofthe present invention, which computer program code may be written in anycombination of one or more programming languages, including an objectoriented programming language such as Java, Scala, Smalltalk, Eiffel,JADE, Emerald, C++, C#, VB.NET, or the like, conventional proceduralprogramming languages, such as the “C” programming language, VisualBasic, Fortran 2003, COBOL 2002, PHP, ABAP, dynamic programminglanguages such as Python, PERL, Ruby, and Groovy, or other programminglanguages.

The at least one processor 4 a may be, or may include, one or moreprogrammable general purpose or special-purpose microprocessors, digitalsignal processors (DSPs), programmable controllers, application specificintegrated circuits (ASICs), programmable logic devices (PLDs),field-programmable gate arrays (FPGAs), trusted platform modules (TPMs),or a combination of such or similar devices, which may be collocated ordistributed across one or more data networks.

Connections between internal components of the controller 4 are shownonly in part and connections between internal components of thecontroller 4 and external components are not shown for clarity, but areprovided by additional components known in the art, such as busses,input/output boards, communication adapters, network adapters, etc. Theconnections between the internal components of the controller 4,therefore, may include, for example, a system bus, a PeripheralComponent Interconnect (PCI) bus or PCI-Express bus, a HyperTransport orindustry standard architecture (ISA) bus, a small computer systeminterface (SCSI) bus, a universal serial bus (USB), IIC (I2C) bus, anAdvanced Technology Attachment (ATA) bus, a Serial ATA (SATA) bus,and/or an Institute of Electrical and Electronics Engineers (IEEE)standard 1394 bus, also called “Firewire.”

The user interface 3 may be of any suitable type. The user interface 3may include a display and/or one or more user input devices. The displaymay be accessible to the at least one processor 4 a via the connectionsbetween the system components. The display may provide graphical userinterfaces for receiving input, displaying intermediate operation/data,and/or exporting output of the methods described herein. The display mayinclude, but is not limited to, a monitor, a touch screen device, etc.,including combinations thereof. The input device may include, but is notlimited to, a mouse, keyboard, camera, etc., including combinationsthereof. The input device may be accessible to the at least oneprocessor 4 a via the connections between the system components. Theuser interface 3 may interface with and/or be operated by computerreadable software code instructions resident in the volatile memory 4 bthat are executed by the processor 4 a.

4. Methods

A non-limiting example of a method of carrying out the present inventionis schematically illustrated in FIG. 2. FIG. 3 illustrates oneembodiment of a product produced by the process of FIG. 2, with exampleintermediate embodiments. FIGS. 4A and 4B illustrate an examplecomputer-generated rendering of a lattice combination and a completedprototype produced by a process of the present invention. In overview,the method of FIG. 2 produces a three-dimensional (3D) object from inputprovided by a user, including desired mechanical properties of the 3Dobject. The 3D object that is produced is a real object that is physicaland tangible, as illustrated, for example, by the prototype of FIG. 4B.The 3D object may be rigid, flexible, or elastic, or any combinationthereof. For example, some portions of the 3D object may be rigid, whileother portions of the 3D object may be flexible. The method may utilizean additive manufacturing apparatus such as, for example, the apparatusillustrated in FIG. 1.

Referring to FIGS. 2 and 3, the method includes an operation in which auser provides 101 characteristics of the 3D object to be manufactured.In some embodiments, the user input 101 may describe a geometry of the3D object. In some embodiments, the geometry of the user input 101 mayinclude a polysurface file (e.g., an .iges file) or a boundaryrepresentation (BREP) file (e.g., a .stl, .obj, .ply, .3mf, .amf, or.mesh file). In some embodiments, the user input 101 may include aboundary shape such as, for example, an outer surface, of the 3D object.In some embodiments, the user input 101 may also include mechanicalproperties of the 3D object. The mechanical properties may include, butare not limited to, descriptions of a flexibility of a portion, or all,of the 3D object, a strength of a portion, or all, of the 3D object,etc. For example, in some embodiments, the user input 101 may specify amechanical property describing a desired flexibility for the 3D object.In some embodiments the user input 101 may specify a first mechanicalproperty describing a desired first flexibility for a first portion ofthe 3D object, and a second mechanical property describing a desiredsecond flexibility for a second portion of the 3D object. That is to saythat the user input 101 may include different mechanical properties fordifferent portions of the 3D object.

The method may also include providing a lattice database 102. Thelattice database 102 may include a plurality (e.g., two or more) oflattice types. For each lattice type, the database may includeinformation about the lattice type including, but not limited to, ageometry of the lattice type, one or more material properties of thelattice type, one or more mechanical properties of the lattice type,and/or a manufacturability score for the lattice type. Themanufacturability score may indicate a metric with respect tomanufacturing the lattice type For example, the manufacturability scoremay indicate a complexity of manufacturing the lattice type, areliability of manufacturing the lattice type, a cost of manufacturingthe lattice type, etc. In some embodiments, a higher manufacturabilityscore may indicate a higher desirability with respect to manufacturingthe given lattice type, though the present invention is not limitedthereto. For example, in some embodiments, a lower manufacturabilityscore may indicate a higher desirability with respect to manufacturingthe given lattice type FIG. 3 illustrates an example of various latticetypes 102′ that may be included as part of the lattice database 102. Thelattice database 102 may be externally provided. In some embodiments,some portion of the lattice database 102 may be provided based onmaterials used to create respective ones of the lattice types. In someembodiments, the lattice database 102 may be capable of being externallyupdated.

As noted above, the user input 101 may include a boundary shape. FIG. 3illustrates an example of a boundary shape 101′ that may be provided bythe user input 101. Within FIG. 3, dashed lines are used to illustrateshapes that may be generated within the memory of a computer, such ascontroller 4 of FIG. 1. Referring again to FIG. 2, in operation 103, theboundary shape 101′ from the user input 101 is subdivided into aplurality (e.g., two or more) work cells. Subdividing the boundary shape101′ may include dividing the boundary shape 101′ into adjacent cells.In some embodiments, the adjacent work cells may each be of a uniformsize. In some embodiments, one or more of the work cells may be of anon-uniform size. FIG. 3 illustrates an intermediate boundary shape 103′which has been subdivided into work cells. Though the embodiment of FIG.3 illustrates work cells which are in a cube shape, it will beunderstood that the present invention is not limited thereto. The workcells may be cubes, cuboids, pyramids, prisms, etc. Similarly, thoughFIG. 3 illustrates work cells of a uniform shape, it will be understoodthat individual ones of the work cells may be different shapes.

Referring again to FIG. 2, in some embodiments the method may continuewith operation 104 in which a start cell of the plurality of work cellsmay be selected. Once the start cell is selected, the start cell may befilled in with a lattice type selected from lattice database 102. Thelattice type selected from the lattice database 102 may be selectedbased, in part, on a comparison of the mechanical properties of thelattice type as retrieved from the lattice database 102 with themechanical properties provided as part of the user input 101. In someembodiments, when more than one lattice type from the lattice database102 meets or exceeds the mechanical properties of the user input 101,the lattice type may be selected based on the manufacturability score ofthe given lattice type. In other words, if multiple lattice types meetthe mechanical properties of the user input 101, the lattice type may beselected based on which lattice type has a more desirable (e.g., ahigher) manufacturing score. FIG. 3 illustrates an example 104′ of theselection of a start cell of the plurality of work cells. Though FIG. 3illustrates a particular start cell with a particular first latticetype, it will be understood that other start cells and/or lattice typesmay be initially selected.

Referring again to FIG. 2, in some embodiments the method may continuewith operation 105 in which the remaining adjacent work cells are filledwith lattice types. The lattice types for the adjacent work cells may beselected based on a comparison of the mechanical property of aparticular lattice type, as retrieved from the lattice database 102, andthe desired mechanical property of the object from the user input 101.In some embodiments, the lattice type for a given work cell may also beselected based on a compatibility of a particular lattice type, asretrieved from the lattice database 102, with the lattice type of anadjacent work cell. Correspondence or compatibility of adjacent latticesin adjacent work cells with one another can be carried out in accordancewith known techniques, or variations thereof that will be apparent tothose skilled in the art. (see, e.g., Z. Karadeniz and D. Kumlutas, Anumerical study on the coefficients of thermal expansion of fiberreinforced composite materials, Composite Structures 78, 1-10 (2007)(three-dimensional FEA unit cell models to predict α₁ and α₂ for severaltypes of composites); V. Liseikin, A computational differential geometryapproach to grid generation (2006)). FIG. 3 illustrates an example 105′in which an example configuration of lattice types have been selectedfor respective ones of the plurality of work cells. The configurationillustrated in FIG. 3 is merely an example, and other configurations arepossible. As illustrated in FIG. 3, an output of operation 105 may be afilled boundary shape 105′ of work cells for manufacture of the 3Dobject.

In some embodiments, as part of filling out the remaining work cells,transitions may be provided between two adjacent work cells havingdifferent lattice types, e.g., first work cell with a first lattice type102 a and second work cell with a second lattice type 102 b. Forexample, the boundary shape 105′ of work cells may be configured suchthat a boundary region 125 between two adjacent work cells having twodifferent lattice types 102 a, 102 b provides interconnections betweenthe two adjacent work cells. Though the boundary region 125 isillustrated as line in FIG. 3, it will be understood that the boundary125 may not be a discrete transition. In some embodiments, the boundary125 may continuously extend over a finite distance between a first workcell and a second work cell. In other words, the boundary 125 may be atransition area between two adjacent work cells and thus may be referredto as a transition segment. In some embodiments, the struts of one workcell (e.g., a first work cell) may be fused to the struts of an adjacentwork cell (e.g., a transition segment). In some embodiments, boundarymorphing may be employed to smooth a surface of an object (e.g., anouter surface of a 3D object) and provide a flat surface seen.

Referring again to FIG. 2, in some embodiments the method may continuewith operation 106 in which the configuration of work cells determinedin operation 105 may be examined for compatibility with desiredmechanical properties of the 3D object. For example, mechanicalproperties of the filled boundary shape 105′ of work cells may beexamined to determine if the mechanical properties are suitable for the3D object. In some embodiments, the desired mechanical properties of the3D object may be based, in part, on the desired mechanical propertiesprovided as part of the user input 101. In some embodiments, testing themechanical properties 106 may involve computer simulation of the filledboundary shape 105′ of work cells based on mathematical and/or empiricalmodels associated with the 3D object.

In some embodiments, if, in operation 106, the mechanical properties ofthe filled boundary shape 105′ are found to be unacceptable (“No” inFIG. 2), the operations may continue with operation 107 in which thefilled boundary shape 105′ is further improved. The improvement 107 mayinclude additional references to the lattice database 102. In someembodiments, the improvement 107 may include changing the configurationof lattice types of one or more work cells the filled boundary shape105′. In some embodiments, the improvement 107 may include starting theprocess described with respect to operation 105 over from the beginningto select a different lattice type for the first work cell. In someembodiments, the improvement 107 may include reconfiguration of thelattice types of a subset of the work cells without changing others ofthe work cells. After the improvement 107 is complete, operation 106 toexamine the mechanical properties of the filled boundary shape 105′ ofthe work cells may be repeated until the mechanical properties are foundto be acceptable (“Yes” in FIG. 2).

In some embodiments, once the mechanical properties of the filledboundary shape 105′ are found to be acceptable, the operations maycontinue with operation 108 in which a final check of manufacturabilitymay be performed. The manufacturability check may include a simulationof the manufacturing process based on the filled boundary shape 105′ ofthe work cells of the 3D object. Manufacturing process simulation can becarried out in accordance with known techniques, or variations thereofthat will be apparent to those skilled in the art (see, e.g., K. Madduxand S. Jain, CAE for the Manufacturing Engineer: The Role of ProcessSimulation in Concurrent Engineering. Advanced Manufacturing Processes1, 365-392 (1986): C. Brauner et al., Meso-level manufacturing processsimulation of sandwich structures to analyze viscoelastic-dependentresidual stresses, Journal of Composite Materials 46, 783-799 (2012); A.Govik et al., Finite element simulation of the manufacturing processchain of a sheet metal assembly, Journal of Materials ProcessingTechnology 212, 1453-1462 (2012); T. Hyodo, Process simulation apparatusand method for selecting an optimum simulation model for a semiconductormanufacturing process U.S. Pat. No. 5,787,269 (1998); N. Ivezic and T.Potok, Method for distributed agent-based non-expert simulation ofmanufacturing process behavior, U.S. Pat. No. 6,826,518 (2004)).

In some embodiments, the boundary object, as modified with theconfiguration of work cells as determined using the methods describedherein, may be used to produce 110 the modified 3D object. Manufacturingof the modified 3D object 110 may be performed, for example, by anadditive manufacturing apparatus, such as that illustrated in FIG. 1.The 3D object may be manufactured to include, in part, a polymer, suchas those described herein. In some embodiments, the additivemanufacturing may be carried out by stereolithography, preferably byCLIP. FIG. 3 illustrates an example of the manufactured 3D object 110′.

FIG. 4A illustrates an example computer-generated rendering of a latticecombination based on embodiments of the processes described herein. FIG.4B illustrates an example completed prototype object 110″ manufacturedbased on the computer-generated rendering of FIG. 4A. FIGS. 4A and 4Bshow the object 110″ that includes two segments having two differentlattice types and a transition segment between the two segments. Thestruts of one segment are fused to the struts of the adjacent segment.In addition, boundary morphing is employed to smooth a surface (e.g., anouter surface) of the object 110″ and provide the flat surface seen.

FIGS. 5-10 show the conversion of an example comer bracket primitive(FIGS. 5 and 8) to a lattice filled object (FIGS. 7 and 10), through apartially converted intermediate illustration thereof (FIGS. 6 and 9).Note the filling with multiple lattices in a compatible format.

Examples of objects that can be produced by the methods of the presentinvention include, but are not limited to, rigid, flexible, and elasticobjects (wholly or partially lattice and with or without a surface“skin” or continuous outer layer over at least a portion thereof formedfrom the same material as the lattice during additive manufacturingthereof), such as wheels, airless tires and component parts thereof,eyeglass frames, seats, seat cushions, bike seats and other saddles,headset cushions, ear buds, shock absorbers, boxing gloves, helmets andhelmet liners, protective pads and protective padding, undergarmentssuch as brassieres and other form-fitting garments, midsoles, braces,beams, frames, etc., any of which can be utilized as formed, or whollyor partially wrapped or covered with another material such as a polymerfilm, woven or nonwoven fabric, leather, etc., including laminatesthereof.

The foregoing is illustrative of the present invention, and is not to beconstrued as limiting thereof. The invention is defined by the followingclaims, with equivalents of the claims to be included therein.

We claim:
 1. A method for producing an object from a light-polymerizableresin by additive manufacturing, comprising: (a) receiving a boundaryshape and a plurality of desired mechanical properties for said objectby a processor: (b) subdividing, by the processor, said boundary shapeinto a plurality of adjacent work cells; (c) providing a plurality oflattices in a database, each lattice of the database including ageometry and a mechanical property; (d) filling a first one of said workcells with a lattice from the database, the lattice selected based on acorrespondence of the mechanical property of said lattice to saiddesired mechanical properties of said object; (e) filling, by theprocessor, remaining ones of said work cells with lattices from saiddatabase to produce a filled boundary shape, each said lattice selectedbased on: (i) the correspondence of the mechanical property of saidlattice to the desired mechanical properties of the object, and (ii)compatibility of adjacent lattices in adjacent work cells with oneanother; and (f) producing said object by additive manufacturing fromthe light-polymerizable resin and the filled boundary shape.
 2. Themethod of claim 1, further comprising, after said filling step (e) thestep of: confirming that the mechanical properties of the lattices ofthe work cells of the filled boundary shape correspond to the desiredmechanical properties for the object, and, if not, then repeating step(e) with different lattices from said database in said work cells untilthe mechanical properties of the filled boundary shape correspond to thedesired mechanical properties of said object.
 3. The method of claim 2,further comprising, prior to said producing step (f), and after saidconfirming step, the step of: performing a manufacturing processsimulation of said filled boundary shape as a check of manufacturabilityof said filled boundary shape.
 4. The method of claim 1, furthercomprising, prior to said producing step (f), the step of: performing amanufacturing process simulation of said filled boundary shape as acheck of manufacturability of said filled boundary shape.
 5. The methodof claim 1, wherein said object is rigid, flexible, or elastic.
 6. Themethod of claim 1, wherein during said producing step (f), surfaceboundaries and/or an outer surface of the object are morphed to smooththe same.
 7. The method of claim 1, wherein said filling step (e)comprises providing a transition segment between two adjacent workcells.
 8. The method of claim 1, wherein the desired mechanicalproperties comprise a flexibility of a first portion of the objectand/or a strength of a second portion of the object.
 9. The method ofclaim 8, wherein the first portion of the object is different from thesecond portion of the object.
 10. An additive manufacturing system forproducing an object from a light-polymerizable resin, the additivemanufacturing system comprising: an additive manufacturing apparatus; aprocessor; and a memory comprising instructions which, when executed bythe processor, cause the processor to control said additivemanufacturing apparatus to perform operations comprising: (a) receivinga boundary shape and a plurality of desired mechanical properties forsaid object; (b) subdividing said boundary shape into a plurality ofadjacent work cells; (c) providing a plurality of lattices in adatabase, each lattice of the database including a geometry and amechanical property; (d) filling a first one of said work cells with alattice from the database, the lattice selected based on acorrespondence of the mechanical property of said lattice to saiddesired mechanical properties of said object; (e) filling remaining onesof said work cells with lattices from said database to produce a filledboundary shape, each said lattice selected based on: (i) thecorrespondence of the mechanical property of said lattice to the desiredmechanical properties of the object, and (ii) compatibility of adjacentlattices in adjacent work cells with one another; and (f) producing saidobject by additive manufacturing from the light-polymerizable resin andthe filled boundary shape.
 11. The additive manufacturing system ofclaim 10, wherein the operations further comprise, after said fillingstep (e) the step of: confirming that the mechanical properties of thelattices of the work cells of the filled boundary shape correspond tothe desired mechanical properties for the object, and, if not, thenrepeating step (e) with different lattices from said database in saidwork cells until the mechanical properties of the filled boundary shapecorrespond to the desired mechanical properties of said object.
 12. Theadditive manufacturing system of claim 11, wherein the operationsfurther comprise, prior to said producing step (f), and after saidconfirming step, the step of: performing a manufacturing processsimulation of said filled boundary shape as a check of manufacturabilityof said filled boundary shape.
 13. The additive manufacturing system ofclaim 10, wherein said object is rigid, flexible, or elastic.
 14. Theadditive manufacturing system of claim 10, wherein during said producingstep (f), surface boundaries and/or an outer surface of the object aremorphed to smooth the same.
 15. The additive manufacturing system ofclaim 10, wherein said filling step (e) comprises providing a transitionsegment between two adjacent work cells.
 16. A computer program productfor producing an object from a light-polymerizable resin, the computerprogram product comprising a non-transitory computer readable storagemedium having computer readable software code sections embodied in themedium, which software code sections are configured to carry outoperations comprising: (a) receiving a boundary shape and a plurality ofdesired mechanical properties for said object by a processor; (b)subdividing, by the processor, said boundary shape into a plurality ofadjacent work cells; (c) providing a plurality of lattices in adatabase, each lattice of the database including a geometry and amechanical property; (d) filling a first one of said work cells with alattice from the database, the lattice selected based on acorrespondence of the mechanical property of said lattice to saiddesired mechanical properties of said object; (e) filling, by theprocessor, remaining ones of said work cells with lattices from saiddatabase to produce a filled boundary shape, each said lattice selectedbased on: (i) the correspondence of the mechanical property of saidlattice to the desired mechanical properties of the object, and (ii)compatibility of adjacent lattices in adjacent work cells with oneanother; and (f) producing said object by additive manufacturing fromthe light-polymerizable resin and the filled boundary shape.
 17. Thecomputer program product of claim 16, wherein the operations furthercomprise, after said filling step (e) the step of: confirming that themechanical properties of the lattices of the work cells of the filledboundary shape correspond to the desired mechanical properties for theobject, and, if not, then repeating step (e) with different latticesfrom said database in said work cells until the mechanical properties ofthe filled boundary shape correspond to the desired mechanicalproperties of said object.
 18. The computer program product of claim 17,wherein the operations further comprise, prior to said producing step(f), and after said confirming step, the step of: performing amanufacturing process simulation of said filled boundary shape as acheck of manufacturability of said filled boundary shape.
 19. Thecomputer program product of claim 16, wherein during said producing step(f), surface boundaries and/or an outer surface of the object aremorphed to smooth the same.
 20. The computer program product of claim16, wherein said filling step (e) comprises providing a transitionsegment between two adjacent work cells.